(1) Field of the Invention
The present invention relates to an automatic electrifier cleaning method suitably applicable to the cleaning of an electrifier (electrifying device) of a printing apparatus based on an electrostatic developing system, and further to an image forming apparatus.
(2) Description of the Related Art
In general, contaminants such as toner and dust float in the interior of a printing apparatus (image forming apparatus), and these contaminants adhere to chassis, corona wires and other parts of a pre-electrifier and a transfer electrifier during the printing operation of the printing apparatus. Further, these contaminants accumulate with the use of the apparatus to cause a reduction of discharge efficiency, the discharge irregularity or the like in the electrifier, which leads to various troubles or problems such as the deterioration of print quality.
For this reason, in order to maintain the print quality of the printing apparatus, a need exists that a maintenance person or the user cleans or replaces the electrifier periodically. This electrifier cleaning work requires considerable skills, for that, for example, its corona wire is constructed using an extremely thin wire having a diameter of approximately 80 .mu.m. Additionally, replacing the electrifier frequently is troublesome, which results in an increase in maintenance cost for the printing apparatus.
Thus, there has been known a printing apparatus which has been made such that a cleaning pad is brought into contact with a corona wire or the like of an electrifier and moved in parallel with the corona wire or the like through the use of a motor or the like to automatically clean the electrifier regularly.
However, in a conventional image forming apparatus, the electrifier is cleaned at a given interval, that is, the electrifier is cleaned automatically even in the case that print paper lies in the vicinity of an image forming drum, with the result that contaminants, such as toner and dust, removed from the electrifier by the cleaning adhere to the paper so that the print quality can deteriorate.
In addition, in the recent years, with the spread of laser printers and others, the using environment of the printing apparatus has come into variety or versatility, and an approach of cleaning the electrifier at a given interval like the above-described conventional automatic electrifier cleaning apparatus cannot remove the contamination of the electrifier sufficiently, thus making it difficult to eliminate various troubles and problems such as the deterioration of print quality resulting from a reduction of discharge efficiency and discharge irregularity of the electrifier.
Conceivably, the period of cleaning the electrifier would be shortened in order to prevent the discharge efficiency reduction and the discharge irregularity of the electrifier. However, this creates a problem in that the wear of its corona wire advances more quickly, which leads to shortening the life of the electrifier.
Still additionally, there is a need to once cease the printing operation of the printing apparatus at the cleaning of the electrifier, and in the case of cleaning the electrifier at a given interval like the conventional automatic electrifier cleaning apparatus, an interruption of the printing operation can take place periodically, which causes a reduction of the printing speed and interferes with the speed-up of the printing processing. This is particularly noticeable in the case of shortening the cycle of the cleaning of the electrifier.